The present invention relates to a terminal unit which is capable of both preparing and editing a document and communicating data with a remote terminal device.
In parallel with the remarkable progress of office automation, there have recently been developed various terminal devices equivalent to a word processor which is capable of advanced data communication in addition to its original function or a telex terminal unit which is capable of document preparation or communication processing in addition to its original function. Such devices may be typified by a communication word processor and a telex terminal unit for international communication.
A document preparing terminal device capable of the two different functions generally comprises an input section equipment with a keyboard for inputting character data, form data and control data necessary for document transmission and system control, a display section having a character display for displaying various data required for document preparation, an output section having a printer for printing out prepared document data and received document data, an external storage section accommodating a floppy disc for storing prepared document data or received document data, a communication control section for controlling the transmission and reception of documents, a section for connecting the terminal device to a communication line, and a system control section for controlling the entire system according to a program. This bifunctional terminal unit, due to its very nature, may receives document data from a remote terminal device while it is operated for preparing a document. It is desirable, therefore, that the terminal unit be capable of delivering the received document either to its output section or external storage without interrupting the preparation of a document.
However, a prior art terminal device of the type described cannot run in parallel a word processing program for preparing a document and a control program for delivering received data to the output section or the external storage. This is because the system control of the prior art device is furnished only with a memory in which a program for running and supervising one program is resident. When document data is received while the device is operating to prepare a document, it cannot be printed out or stored immediately but has to be done so after the document preparation or interrupting it.
Another drawback is that when the printing operation is disabled due to a failure in a printer or the like during reception of a document or waiting period, "failure" or "reception unable" is displayed after the memory of the communication control has become full. This makes it impossible to receive any further document data.
Furthermore, such a terminal device is made up of a number of equipments which are usually connected to a common power source to be constantly supplied with power. This degrades the durability and reliability of various equipments for which the constant supply of power is needless, particularly those constituting the input section, display section and external storage, while inviting wasteful consumption of power.